It is very dangerous to install electronic devices such as an electronic sensor or lamp in a fuel gauge since the gauge measures the amount of gasoline which is a very explosive material.
A conventional fuel gauge is provided with a floating body containing air. The location of the floating body varies in accordance with the amount of fuel contained in a fuel tank. The variation induces resistance variation in a resistor which is provided at the end of the floating body, thereby indicating the fuel amount contained in the fuel tank.
However, the prior art has the following problems.
First, some contaminants affect the buoyancy of the floating body, thereby causing error or malfunction of the gauge.
Second, the varying resistor whose resistance varies in accordance with the floating location of the floating body has a problem of frequent error or malfunction due to corrosion of contact points of the resistor.
Therefore, of interest is a new gauge which does not need the floating body and the varying resistor. Further, it has been desired to provide an apparatus for measuring fuel amount, which does not comprise electronic devices such as an electronic sensor, lamp and the like since the material to be measured is a fuel such as gasoline that is very explosive.